Cordless phone system capable of scrambling communication signals

ABSTRACT

A cordless phone system includes a first cordless phone and a second cordless phone which are coupled to each other by a network, the first cordless phone being formed of a first personal station and a first base station, the second cordless phone being formed of a second personal station and a second base station. The cordless phone includes a scrambler, provided in the first personal station, for scrambling communication signals in a predetermined scrambling manner, the communication signals scrambled by the scrambler being transmitted from the first personal station to the first base station in radio, a first relay circuit, provided in the first base station, for receiving the communication signals from the first personal station and for transmitting the communication signals, without descrambling, to the second base station via the network, a second relay circuit, provided in the second base station, for receiving the communication signals from the first base station and for transmitting the communication signals, without scrambling, to the second personal station in radio; and a descrambler, provided in the second personal station, for descrambling the communication signals transmitted from the second base station in radio in a predetermined descrambling manner corresponding to the scrambling manner in the first personal station, so that original communication signals are restored.

This is a division of application Ser. No. 07/968,982, filed Oct. 30,1992, which was allowed, now U.S. Pat. No. 5,392,354.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention generally relates to a cordless phone systemcapable of scrambling communication signals, and more particularly to acordless phone system capable of scrambling communication signals inwhich system communication quality can be prevented from deterioratingby scrambling.

(2) Description of Related Art

Recently, cordless phones have been spread. The cordless phones can betapped by other persons. Thus, to prevent from being tapped, ascrambling technique has been applied to the cordless phones.

Communication signals to be transmitted in radio are scrambled by ascrambler, for example, as shown in FIG. 1A. This scrambler inverts thefrequency spectrum of the input signals and outputs inverted signalshaving an inverted frequency spectrum, so that the input signals arescrambled. This type of scrambling manner is often referred to as afrequency inversion method.

Referring to FIG. 1A, an input communication signal is supplied to afirst low pass filter (LPF) 40, and only frequency components, of theinput signal, within a range between a higher cut-off frequency f2 (e.g.3300 Hz) and a lower cut-off frequency f1 (e.g. 300 Hz) pass through thefirst low pass filter 40. As a result, the frequency spectrum as shownin FIG. 1B is obtained at an output point (A) of the first low passfilter 40. The communication signal output from the first low passfilter 40 is supplied to a modulator 41. The modulator 41 modulates acarrier having a frequency fm based on the communication signal suppliedfrom the first low pass filter 40, so that two frequency spectrums asshown in FIG. 1C are obtained at an output point (B) of the modulator41. The first frequency spectrum is in a frequency range between (f2-fm)and (f1-fm), and the second frequency spectrum is in a frequency rangebetween (f1+fm) and (f2+fm). The output signal from the modulator 41 issupplied to a second low pass filter 42, and frequency components inonly the first frequency spectrum can pass through the second low passfilter 42. As a result, a frequency spectrum as shown in FIG. 1D isobtained at an output point (C) of the second low pass filter 42. Thatis, this scrambler outputs an inverted signal having a frequencyspectrum as shown in FIG. 1D.

The inverted signal output from the scrambler is modulated in accordancewith a frequency modulation (FM) process at a radio frequency of a radiochannel, and the modulated signal is transmitted, as a radio signal, viathe radio channel. The radio signal is demodulated in a receiver, andthen the signal having the inverted frequency spectrum is modulatedbased on the carrier (fm), so that the signal having an originalfrequency spectrum is restored. Then the communication signal isobtained.

There are various well-known scrambling manners other than the abovefrequency inversion method, referred to, for example, as a method inwhich the radio channel is changed during communication.

FIG. 2 shows a conventional cordless phone system capable of scramblingcommunication signals.

Referring to FIG. 2, a first cordless phone comprises a personal stationA and a base station A. The base station A is coupled to a public datanetwork (e.g. an ISDN or a private network). A second cordless phonecomprises a personal station B and a base station B. The base station Bis also coupled to the public data network, so that the base stations Aand B of the first and second cordless phones are coupled to each othervia the public data network. In this conventional cordless phone system,a communication signal corresponding to speech of a user is scrambled inthe personal station A of the first cordless phone (a), and thescrambled communication signal is transmitted from the personal stationA to the base station A via a predetermined radio channel. The scrambledcommunication signal received by the base station is descrambled so thatthe original communication signal is restored (b). The communicationsignal output from the base station A of the first cordless phone istransmitted to the base station B of the second cordless phone via thepublic data network. The communication signal received by the basestation B of the second cordless phone is scrambled again (c), and thescrambled communication signal is transmitted from the base station B tothe personal station B via a predetermined radio channel. The scrambledcommunication signal received by the personal station B of the secondcordless phone is descrambled again (d), and the original communicationsignal is restored. Then the personal station B of the second cordlessphone reproduces speech base on the restored communication signal. In acase where the communication signal is transmitted from the personalstation B of the second cordless phone, the personal station B scramblesthe communication signal (e), the base station B of the second cordlessphone descrambles the scrambled communication signal (f), the basestation A of the first cordless phone scrambles the receivedcommunication signal again (g), and the personal station A of the firstcordless phone descrambles the scrambled communication signal again (h),in the same manner as those in the above case where the communicationsignal is transmitted from the personal station of the first cordlessphone.

In the above conventional cordless phone system, the first cordlessphone comprising the personal station A and the base station A carriesout both a scrambling process and a corresponding descrambling process.The second cordless phone also carries out both a scrambling process anda corresponding descrambling process. Frequency characteristics ofcommunication signals are changed every time the scrambling ordescrambling process is performed. Thus, as a large number of scramblingand the descrambling processes are performed in the conventionalcordless phone system, communication quality between the personalstations deteriorates in comparison with the communication qualitywithout scrambling.

SUMMARY OF THE INVENTION

Accordingly, a general object of the present invention is to provide acordless phone system capable of scrambling in which the disadvantagesof the aforementioned prior art are eliminated.

A more specific object of the present invention is to provide a cordlessphone system capable of scrambling in which system communication qualitycan be prevented from deteriorating in the communication betweenpersonal stations.

The above objects of the present invention are achieved by a cordlessphone system having a first cordless phone and a second cordless phonewhich are coupled to each other by a network, the first cordless phonebeing formed of a first personal station and a first base station, thesecond cordless phone being formed of a second personal station and asecond base station, the cordless phone comprising: scrambling means,provided in the first personal station, for scrambling communicationsignals in a predetermined scrambling manner, the communication signalsscrambled by the scrambling means being transmitted from the firstpersonal station to the first base station in radio; first relay means,provided in the first base station, for receiving the communicationsignals from the first personal station and for transmitting thecommunication signals, without descrambling, to the second base stationvia the network; second relay means, provided in the second basestation, for receiving the communication signals from the first basestation and for transmitting the communication signals, withoutscrambling, to the second personal station in radio; and descramblingmeans, provided in the second personal station, for descrambling thecommunication signals transmitted from the second base station in radioin a predetermined descrambling manner corresponding to the scramblingmanner in the first personal station, so that original communicationsignals originated by the first personal station are restored.

According to the present invention, in the communication between thefirst and second personal stations, the scrambling and descramblingprocesses are performed once only. Thus, the communication qualitydeteriorates little.

Additional objects, features and advantages of the present inventionwill become apparent from the following detailed description when readin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram illustrating an example of a conventionalscrambler.

FIGS. 1B, 1C and 1D are graphs illustrating frequency spectrum atvarious points in the scrambler shown in FIG. 1A.

FIG. 2 is a diagram illustrating a conventional cordless phone system.

FIG. 3 is a block diagram illustrating an essential part of a cordlessphone system according to a first embodiment of the present invention.

FIG. 4 is a block diagram illustrating a personal station provided inthe cordless phone system according to the first embodiment of thepresent invention.

FIG. 5 is a flow chart illustrating process carried out in the cordlessphone system shown in FIGS. 3 and 4.

FIG. 6 is a diagram illustrating a cordless phone system according tothe embodiment of a second present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A description will now be given, with reference to FIG. 3, of theprinciple of an embodiment of the present invention.

Referring to FIG. 3, a first cordless phone 100 comprises a personalstation 1 and a base station 3. Radio communication is performed betweenthe personal station 1 and the base station 3. The base station 3 iscoupled to a network 7 (including a PBX network, an ISDN or the like) bya cable. A second cordless phone 300 comprises a personal station 12 anda base station 8 coupled to the network 7 by a cable. The personalstations 1 and 12 respectively have privacy communication units 2 and 13each of which has a scrambler and a descrambler. The base stations 3 and8 respectively have privacy communication units 4 and 9, selectors 5 and10, and controllers 6 and 11. The controllers 6 and 9 respectivelycontrol the selectors 5 and 10 so that the selectors 5 and 10 selectoutput ports of the privacy communication units 4 and 9 or input portsof the privacy communication units 4 and 9.

When the personal station 1 of the first cordless phone 100 dials thesecond cordless phone 300, the personal station 12 of the secondcordless phone 300 is called in via the network 7 and the base station 8of the second cordless phone 300. Then, when an operation of thepersonal station 12 is performed in response to the call in, thecommunication between the personal stations 1 and 12 can be performed.The controller 6 determines whether or not the second cordless phone 300scrambles communication signals in the same scrambling manner as thefirst cordless phone 100. When the second cordless phone 300 scramblesthe communication signals in the same scrambling manner as the firstcordless phone 100, the controller 6 makes the selector 5 to select theinput port of the privacy communication unit 4. As a result, thescrambled communication signal supplied from the personal station 1 inradio is transmitted to the base station 8 of the second cordless phone300 via the selector 5 and the network 7 without descrambling. In thebase station 8 of the second cordless phone 300, the controller 11determines whether or not the first cordless phone 100 scramblescommunication signals in the same scrambling manner as the secondcordless phone 300. When the controller 11 determines that the firstcordless phone 100 scrambles the communication signals in the samescrambling manner as the second cordless phone 300, the controller 11makes the selector 10 to select the input port of the privacycommunication unit 9. As a result, the scrambled communication signalreceived by the base station 8 is transmitted to the personal station 12of the second cordless phone 300 without scrambling in radio. Theprivacy communication unit 13 of the personal station 12 descrambles thescrambled communication signal transmitted from the base station 8, sothat the original communication signal is restored in the personalstation 12 of the second cordless phone 300.

In the above cordless phone system, when the communication is performedbetween the personal stations 1 and 12 of the first and second cordlessphones 100 and 300 with scrambling, each of the scrambling process andthe descrambling process is performed at only one time. The number oftimes that the communication signals are scrambled and descrambled aredecreased. Thus, the communication quality deteriorates little.

The controller 6 of the base station 3 of the first cordless phone 100has, for example, a storage for storing phone numbers each specifying acordless phone in which communication signals are scrambled in the samescrambling manner as the first cordless phone 100. In this case,controller 6 determines, with reference to the phone numbers stored inthe storage, whether or not the communication signals are scrambled inthe second cordless phone 300 in the same scrambling manner as the firstcordless phone 100. The controller 11 of the base station 8 of thesecond cordless phone 300 also has a storage for storing phone numbersspecifying cordless phones in which the communication signals arescrambled in the same scrambling manner as the second cordless phone300.

Scrambling manners of cordless phones coupled to the network 7 may bealso recorded. In this case, when the first cordless phone 100communicates with the second cordless phone 300, the network 7 informsthe first and second cordless phones 100 and 300 of the scramblingmanners to be carried out in the second and first cordless phones 300and 100. When the controllers 6 and 11 determine that the scramblingmanners respectively carried out in the first and second cordless phones100 and 300 are equal to the scrambling manners informed by the network,the controllers 6 and 11 make the selectors 5 and 10 to select the inputports of the privacy communication units 4 and 9. On the other hand,when the controllers 6 and 11 determine that the scrambling manners tobe carried out in the first and second cordless phones 100 and 300differ from the scrambling manners informed by the network 7, thecontroller 6 and 11 make the selectors 5 and 10 to select the outputports of the privacy communication units 4 and 9.

A description will now be given, with reference to FIGS. 4, 5 and 6, ofthe embodiment of the present invention.

FIG. 4 shows a base station of a cordless phone. A base station 20 shownin FIG. 4 is coupled to a network (e.g. a public data network, apersonal network, or an ISDN) by a cable formed of, for example, opticalfibers. The base station 20 is also coupled to a personal station inradio. Referring to FIG. 4, the base station 20 comprises a radio unit200, a distribution circuit 201, selectors 202 and 207, a descrambler204, OR gates 205 and 210, a speech network 206 and scrambler 208. Thebase station 20 further comprises a key-board 211, controller 212 andmemory unit 213. The radio unit 200 controls transmission and receipt ofcommunication signals and control signals in radio communication withrespect to the personal station. The distribution circuit 201 suppliesphone number information in the communication signals supplied from thepersonal station via the radio unit 200 to the controller 212. Otherinformation in the communication signals pass through the distributioncircuit 201. The selector 202 selects either a path 203 or thedescrambler 204, so that the communication signals supplied from thedistribution circuit 201 is supplied to selected one of the path 203 andthe descrambler 204. The communication signals from the path 203 and thedescrambler 204 are supplied to the speech network via the OR gate 205.The speech network 206 is coupled to a public data network. The selector207 selects either a path 209 or the scrambler 208, so thatcommunication signals supplied from the public data network via thespeech network 206 is supplied to selected one of the path 209 and thescrambler 208. The communication signals from the path 209 and thescrambler 208 are supplied to the radio unit 200 via the OR gate 210.The key-board 211 is operated to input information such as phonenumbers. The controller 212 controls whole parts of the base station 20.The memory unit 213 has a ROM (Read Only Memory) and a RAM (RandomAccess Memory) and like. The memory unit 213 stores control programsused in the controller 212 and various control information. The memoryunit 213 further stores a table indicating phone numbers specifyingother cordless phones processing communication signals in the samescrambling manner as this base station 20. A network termination unit(not shown in FIG. 4) for the ISDN is provided between the base station20 and the public data network.

Communication between the first and second cordless phones is performedin accordance with a flow chart as shown in FIG. 5.

When the personal phone of the first cordless phone originates a call,the radio unit 200 of the base station 20 receives calling information(dialing information (a phone number), call control information of theISDN and the like). The controller 212 then controls the selector 202 sothat the path 203 is selected. The calling information is output to thepublic data network via the speech network 206. The calling informationis transmitted to the base station 20 of the second cordless phone viathe public data network, and the second cordless phone is called in.When a predetermined operation is performed in the second cordless phonein response to the call from the first cordless phone, the first andsecond cordless phone are in a state where communication can beperformed. After this, the communication between the first and secondcordless phone is performed in accordance with the flow chart shown inFIG. 5.

The personal station of the first cordless phone scrambles communicationsignals in a predetermined scrambling manner, and the scrambledcommunication signals are transmitted from the personal station in radio(step S1). The scrambled communication signals from the personal stationare received by the radio unit 200 of the base station 20 of the firstcordless phone (step S2). In the base station 20 of the first cordlessphone, controller 212 determines, based on scrambling informationtransmitted from the personal station along with the communicationsignals, whether or not the received communication signals are scrambled(step S3). When the controller 212 determines that the receivedcommunication signals are scrambled, in step S3, the controller 212determines, with reference to the table stored in the memory unit 213,whether or not the phone number included in the calling information isequal to one of the phone numbers indicated in the table (step S4). Thatis, step S4 determines whether or not the second cordless phone (thecalled station) scrambles communication signals in the same scramblingmanner as the first cordless phone (the calling station). The resultobtained by step S4 is YES, the controller 212 controls the selector 202so that the path 203 is selected. As a result, the scrambledcommunication signals received by the radio unit 200 are supplied to thepublic data network via the distribution circuit 201, the selector 202,the OR gate 205 and the speech network 206 (step S7). Then the scrambledcommunication signals are transmitted to the base station 20 of thesecond cordless phone. At this time, the controller 212 controls theselector 207 so that the path 209 is selected. Thus, the speech network206 is coupled to the radio unit 200 via the selector 207, the path 209and the OR gate 210.

In the base station 20 of the second cordless phone, when the speechnetwork 206 receives the scrambled communication signals transmittedfrom the first cordless phone, the controller 212 determines whetherthis call is originated by the base station of the first cordless phoneor the personal station thereof (step S8). When the controller 212determines that this call is originated by the personals station, thecontroller 212 further whether or not the received communication signalsare scrambled (step S9). When the result obtained by step S9 is YES, thecontroller 212 determines, with reference to the table stored in thememory unit 213, whether or not the phone number of the first cordlessphone (the calling station) is equal to one of the phone numbersindicated in the table (step S10). That is, step S10 determines whetheror not the first cordless phone (the calling station) scramblescommunication signals in the same scrambling manner as the secondcordless phone *the called station). When the result obtained by stepstep S10 is YES, the controller 212 controls the selector 207 so thatthe path 209 is selected. As a result, the scrambled communicationsignals received by the speech network 206 are supplied to the radiounit 200 via the selector 207, the path 209 and the OR gate 210 so thatthe scrambling operation in the second cordless phone is cancelled (stepS11). Then the scrambled communication signals are transmitted from theradio unit 200 in radio (step S12). The scrambled communication signalstransmitted from the radio unit 200 are received by the personal stationof the second cordless phone (step S13). In the personal station of thesecond cordless phone, the received scrambled communication aredescrambled. In this case, as the scrambling manner of the secondcordless phone is the same as that of the first cordless phone, theoriginal communication signals which have been transmitted from thepersonal station of the first cordless phone are restored by thedescrambling operation in the personal station of the second cordlessphone.

Communication signals made in the personal station of the secondcordless phone in response to the communication signals transmitted fromthe first cordless phone are processed in the same manner as in theabove case, and returned to the first cordless phone.

On the other hand, when the controller 212 of the base station 20 of thefirst cordless phone (the calling station) determines that there is nophone number being the same as the phone number of the second cordlessphone in the stable, in step S4, the controller 212 controls theselector 202 so that the descrambler 204 is selected. As a result, thescrambled communication signals output from the radio unit 200 isdescrambled by the descrambler 204 (step S5). The communication signals(the original signals) output from the descrambler 204 are supplied tothe public data network via the OR gate 205 and the speech network 206(step S7). The controller 212 controls also the selector 207 so that thescrambler 208 is selected.

In the base station 20 of the second cordless phone (the calledstation), when the speech network 206 receives the communicationsignals, step S9 determines that the communication signals are notscrambled. Thus the controller 212 controls the selector 207 so that thescrambler 208 is selected (step S14). As a result, the communicationsignals received by the speech network 206 are scrambled by thescrambler 208 and supplied to the radio unit 200 via the OR gate 210.The scrambled communication signals are transmitted from the radio unit200 in radio (step S12). The personal station of the second cordlessphone receives the scrambled communication signals transmitted from thebase station 20 (step S13). The scrambled communication signals aredescrambled in the personal station, so that the original communicationstation are restored.

Further, in a case where the base station of the first cordless phoneoriginates a call of the second cordless phone, communication signalscorresponding to speech of a user are also originated in the basestation of the first cordless phone (step S6). After this, thecommunication signals are output from the speech network to the publicdata network without scrambling (step S7). In this case, in the basestation 20 of the second cordless phone (the called station), thecontroller 212 determines that this call is originated by the basestation 20 of the first cordless phone (step S8). Then, thecommunication signals received by the base station 20 of the secondcordless phone are scrambled (step S14) and then transmitted from theradio unit 200 in radio (step S12). The scrambled communication signalsreceived by the personal station of the second cordless phone aredescrambled, so that the original communication signals are restored.

A description will now be given, with reference to FIG. 6, of a secondembodiment of the present invention.

Referring to FIG. 6, a cordless phone system has first, second and thirdcordless phones (A), (B) and (C) and a normal telephone set 37. Thefirst, second and third cordless phones (A), (B) and (C) arerespectively consisted of a personal stations 30, 36 and 39 and basestations 31, 35 and 38. The base stations 31, 35 and 38 and thetelephone set 37 are coupled to a network 32 (a public data network, apersonal network, an ISDN, or the like) by cables. This cordless phonesystem also has a controller 33 for controlling the network 32 and amemory unit 34 coupled to the controller 34. The memory unit 34 stores atable indicating types of scrambling manners in the first, second andthird cordless phones (A), (B) and (C). In this table, the phone numbersspecifying the first, second and third cordless phones respectivelycorrespond to types of scrambling manner.

In the second embodiment, when communication between a cordless phoneand another one is performed via the network 32, the controller 33controls whether or not communication signals transmitted from a basestation to another one via the network are scrambled.

The personal station 30 of the first cordless phone (A) originates acall to, for example, the second cordless phone (B). When originatingthe call, the base station 31 of the first cordless phone (A) transmitscalling information to the network 32. The calling information issupplied to the controller 33 via the network 32. The controller 33controls the network 32 so that the first and second cordless phones (A)and (B) are connected by the network 32. If the second cordless phone(B) is not busy, the controller 33 controls the network to call thesecond cordless phone (B). The controller 33 determines, with referenceto the table stored in the memory unit 34, whether or not a scramblingmanner corresponding to the phone number of the first cordless phone (A)is the same as a scrambling manner corresponding to the phone number ofthe second cordless phone (B). When the controller 33 determines thatthe scrambling manner of the first cordless phone (A) is the same asthat of the second cordless phone (B), the controller 33 supplies to thebase stations 31 and 35 of the first and second cordless phone (A) and(B) via the network 32 control signals for cancelling descrambleoperations in the base stations 31 and 35. As a result, communicationsignals scrambled by the personal station 30 of the first cordless phone(A) is supplied to the personal station 36 of the second cordless phone(B) via the base station 31 of the first cordless phone (A), the network32 and the base station 35 of the second cordless phone (B), without thedescrambling operation and the scrambling operation (see 1 shown in FIG.6). The personal station 36 of the second cordless phone (B) thendescrambles the scrambled communication signals transmitted from thebase station 35 in radio, so that the original communication signals areobtained in the personal station 36 of the second cordless phone (B).

When the controller 33 detects a call from the first cordless phone (A)to the third cordless phone (C), the controller 33 determines, withreference to the table stored in the memory unit 34, whether or not atype of the scrambling manner corresponding to the first cordless phone(A) is the same as that of the third cordless phone (C). When thecontroller 33 determines that the scrambling manner of the firstcordless phone (A) is not the same as that of the third cordless phone(C), the controller 33 supplies no control signals to the base stations31 and 38 of the first and third cordless phone. Thus, the scrambledcommunication signals transmitted from the personal station 30 isdescrambled in the base station 31 of the first cordless phone (A). Thecommunication signals transmitted to the base station 38 of the thirdcordless phone (C) via the network 32 is scrambled in a predeterminedscrambling manner. The scrambled communication signals are thentransmitted from the base station 38 in radio. The scrambledcommunication signals are descrambled in the personal station 39 of thethird cordless phone (C), so that the original communication signals arerestored in the personal station 39.

In a case where the first cordless phone (A) calls the telephone set 37,the controller 33 controls the base station 31 of the first cordlessphone (A) so that the scrambled communication signals are descrambled inthe base station 31.

States of the communication signals in the above cases where the firstcordless phone (A) calls the third cordless phone (C) or the telephoneset 37 are indicated by 2 in FIG. 6.

The present invention is not limited to the aforementioned embodiments,and variation and modifications may be made without departing from thescope of the claimed invention.

What is claimed is:
 1. A base station of a cordless phone, forcommunicating with a personal station of the cordless phone by radio andbeing connected to a network, said base station comprising:receivingmeans for receiving a scrambled signal transmitted by radio from saidpersonal station; and output means for outputting the scrambled signalreceived by said receiving means to said network without descramblingwhen a scrambling manner of the scrambled signal transmitted by radiofrom said personal station is the same as a scrambling manner ofcommunication signals in another phone communicated with said cordlessphone via said network.
 2. A base station of a cordless phone, forcommunicating with a personal station of the cordless phone by radio andbeing connected to a network, said base station comprising:receivingmeans for receiving a scrambled signal transmitted by radio from saidpersonal station; descrambling means for descrambling the scrambledsignal received by said receiving means; output means for outputting thescrambled signal received by said receiving means without descrambling;selecting means for selecting either a signal obtained by saiddescrambling means or the scrambled signal output by said output means,a signal selected by said selecting means being supplied to saidnetwork; and control means for controlling a selecting operation of saidselecting means.
 3. The base station as claimed in claim 2, wherein whena scrambling manner of the scrambled signal transmitted by radio by saidpersonal station is the same as a scrambling manner in another phonecommunicated with said cordless phone via said network, said controlmeans causes said selecting means to select the scrambled signal outputby said output means.
 4. The base station as claimed in claim 3; andfurther comprising storage means for recording destinations of otherphones, in each of which signals are scrambled using a scrambling mannerwhich is the same as the scrambling manner for the scrambled signaltransmitted from said personal station of said cordless phone, whereinwhen said cordless phone communicates via said network with anotherphone of a destination recorded in said storage means, said controlmeans causes said selecting means to select the scrambled signal outputby said output means.
 5. A base station of a cordless phone, forcommunicating with a personal station of the cordless phone by radio andbeing connected to a network, said base station comprising:receivingmeans for receiving a scrambled signal transmitted through said network;and transmission means for transmitting by radio the scrambled signalreceived by said receiving means to said personal station withoutscrambling when the signal received by said receiving means is scrambledin a scrambling manner which is the same as a scrambling manner used insaid cordless phone.
 6. A base station of a cordless p hone, forcommunication with a personal station of the cordless phone by radio andbeing connected to a network, said base station comprising:receivingmeans for receiving a signal transmitted through said network;transmission means for transmitting the signal received by saidreceiving means to said personal station without scrambling; scramblingmeans for scrambling the signal received by said receiving means and fortransmitting by radio a scrambled signal to said personal station;selecting means for selecting either said transmission means or saidscrambling means, a signal selected by said selecting means beingtransmitted by radio to said personal station; and control means forcontrolling a selecting operation of said selecting means.
 7. The basestation as claimed in claim 6, wherein when the signal received by saidreceiving means is scrambled using a scrambling manner which is the sameas a scrambling manner of said scrambling means, said control meanscauses said selecting means to select said transmission means.
 8. Thebase station claimed in claim 7, and further comprising storage meansfor recording calling stations in each of which signals are scrambledusing the same scrambling manner as that used by said scrambling means,wherein when said cordless phone communicates with a calling stationrecorded in said storage means, said control means causes said selectingmeans to select said transmission means.